In the paint and coating fields, it is lately required from the standpoints of avoiding environmental pollution and maintaining a safe working environment, to change the dispersing media from organic solvents to aqueous media. To meet the requirement, emulsion type coating compositions having radical polymerizable vinyl monomers emulsion polymerized as typified by acrylic resins are widely utilized as the base material of coating compositions because of their film formability and chemical resistance. The coating compositions of this type, however, have the drawback that they are essentially less resistant to water and weather.
On the other hand, silicone resins which are obtained through hydrolysis and condensation of silane compounds draw attention as coating compositions because they are able to form films having a high hardness and exhibiting good properties including weather resistance, water resistance, heat resistance and water repellency. However, the emulsion polymerization process of obtaining silicone resin by polymerizing monomers in emulsion has not been established. As the general rule, silicone resin solutions are prepared in organic solvent systems such as toluene and xylene and then emulsified without isolation.
Instability is one problem associated with these organic solvent-containing silicone resin emulsions. In addition, the environmental concern requires to control the use of organic solvents such as toluene and xylene.
The patent publications pertinent to the present invention include JP-A 6-172649 (U.S. Pat. No. 5,264,027), JP-A 7-247434, JP-A 7-316432, and JP-A 2000-63756.